AFAIK that's not really true, europeans are not usually highly embalmed but they're mostly buried in coffins in vaults rented for years or decades (depending on the country).
AFAIK https://i2.wp.com/www.talkdeath.com/wp-content/uploads/2018/... is a pretty typical-looking cemetery for western europe at least (some countries tend towards just the headstone and no vault, but as an other commenter notes that doesn't mean the body readily decomposes either)
Those are not vaults. Those are just holes in ground with a cover on top. It's mostly decorative and there so that you don't walk on top of the coffin.
We don't usually own these also. Usually city where you live has a cemetery that must provide a place for the coffin.
That would apply to municipal graveyard while church owned ones are managed separately. In either case, if grave spot fee isn't paid on time, space goes back to the pool while remains of previous "occupant" are transferred to the ossuarium - IIRC.